Dredge first

The area between the Siquieros and Clipperton Transforms on the East Pacific Rise at 8-10°N (often referred to as 9°N ) has been a focus of intense study over the past 10 years. The first U-series work in this area involved combined °Th and Pa analyses of samples collected by submersible, rock coring and dredging along the southern portion of 9°N (Goldstein et al. 1993) (Fig. 3). Volpe and Goldstein (1993) analyzed three of these... 

This relationship has been predicted by the stellar evolution theory, as resulting essentially from the so called first and second dredge-up episodes. In Fig. la we see the corresponding predictions by the theory (Marigo, 2001). The sensitivity of the predicted abundances both to the metallicity at the epoch of formation of the progenitors and to their stellar mass in the Main Sequence is evident, making such diagrams powerful tools to trace back the evolutionary history of individual PNe. Uncertainties prevent however us to pursue now this... 

As can be seen in Table 1, all the program clusters also show very low 12C/13C isotopic ratios, which cannot be explained by first-dredge up alone, but they... 

Rotational mixing does not affect significantly the stellar structure (Lbump is the same in models A, B and C), but leads to larger abundance variations on the lower RGB associated with a deeper first dredge-up (Fig. lb). 

The sodium yields are also different in the FST model sodium is first created and the destroyed, when the Ne-Na cycle becomes fully operative. In the MLT models the 3rd dredge-up becomes so efficient that Sodium is eventually produced due to 22 Ne burning in the MLT framework the AGB ejecta are expected to have great mass fractions of sodium. 

Fig. 5.7. Evolutionary tracks for Z = 0.02 (near solar metallicity) stars with different masses in the HR diagram. (Luminosities are in solar units.) Points labelled 1 define the ZAMS and points labelled 2 the terminal main sequence (TAMS), the point where central hydrogen is exhausted. The Schonberg-Chandrasekhar limit may be reached either before or after this (for M > 1.4 Af0). Points marked 3 show the onset of shell hydrogen-burning. Few stars are found in the Hertzsprung gap between point 4 and point 5 , where the surface convection zone has grown deep enough to bring nuclear processed material to the surface in the first dredge-up. Adapted from Iben (1967).

Intermediate-mass stars with A/imt > 3 to a mass Mup somewhere between 5 and 8 M0, depending on chemical composition and evolutionary details, undergo three dredge-up episodes in the course of evolution, the first one during the first... 

If river cleanup is involved, including dredging, the first estimate of the costs likely to be incurred is on the order of 6.6 Million per kilometer. This includes dredging the bottoms, cleaning and excavating the sides, and thermally treating the sludges after they are dewatered. The sediments will be pumped out at about 2% solids and have to be put into a contained area, the liquid treated, and the solids dried and excavated. 

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